The FIR was filed by the central crime police based on the complaint of PRO K Muralidhar on July 14.
According to the complaint, Muralidhar received the threat message on his WhatsApp from an international number on his official mobile phone around 7 pm on July 12.
The message was written in Hindi, Urdu, and English by a Dubai gang allegedly threatening to kill Muralidhar and six High Court judges.
The judges on target are: Justice Mohammed Nawaz, Justice HT Narendra Prasad, Justice Ashok G Nijagannavar (retired), Justice HP Sandesh, Justice K Natarajan and Justice B Veerappa (retired).
The FIR has been registered under sections 506, 507 and 504 of the IPC and sections 75 and 66(F) of the IT Act, the police said.
[With UNI inputs]